Electrodynamic circuit breaker



Dec. 8, 1959 F. KESSELRING ETAL 2,916,579

ELECTRODYNAMIC CIRCUIT BREAKER Filed Jan. 11, 1956 /e m X Q1; 15 /A mVHVTO S FZ/Tz 'ssEL /A G fawn/20 Jaws M51010 United States PatentELECTRODYNAMIC CIRCUIT BREAKER Fritz Kesselring, Zollikon Zurich,Switzerland, and Edward John Diebold, Ardmore, Pa.; said Kesselringassignor to Siemens-Schuckertwerke A.G., Berlin, Germany, a corporationof Germany, and said Diebold assignor to I-T-E Circuit Breaker Company,Philadelphia, Pa., a corporation of Pennsylvania Application January 11,1956, Serial No. 558,522

Claims priority, application Germany January 13, 1955 9 Claims. (Cl.200-87) Our invention relates to an electrodynamic circuit breaker ofthe type described in copending application Serial No. 558,349, filedJanuary 10, 1956, and assigned to the assignee of the instant inventionand more particularly to an electromagnetic circuit breaker wherein therelation:

holds true and is achieved within fractions of a millisecond with theabove quantities to be defined hereinafter.

The above noted application Serial No. 558,349 more specifically shows acontacting device in which a unitary member serves as a movable contactfor a pair of cooperating contacts as well as a winding which is sodisposed as to interact with a second or operating winding, theenergization of which will give rise to magnetic fields in both themovable contact winding and the operating winding which are so directedas to cause the movable contact to move with relation to its cooperatingcontact.

We have, however, found that for optimum operation of devices of theabove described type that the relation:

HOIINIJ 21raa'y should be achieved within a fraction of a millisecond,where I is the peak current in the operating Winding in amperes N is thenumber of turns of the operating winding, I is the current density inthe operating wind ing in amperes per square meter, a is the effectivecoupling distance between the operating winding and the movable contactWinding in meters, 7 is the weight density of the current carryingmaterial in kilograms per cubic meter and a is a correction factor to beused when a mass other than the mass of the movable contact is to beaccelerated, and n is the permeability of free space in volt seconds perampere meter or More specifically, the correction factor a is given by 2where m, is the mass of an additional body attached to the movablecontact and m is the mass of the contact ring or winding, bothquantities being expressed in kilogram seconds squared per meter.

The derivation of the above relationship will be given hereinafter andmay be applied to any form or structure which operates in accordancewith the above noted principle.

Accordingly, the primary object of our invention is to provide acontacting device in which the movable contact of the contacting deviceis constructed to form 2,916,579 Patented Dec. 8, 1959 teract with asecond energizable winding whereby motion of the movable contact isobtained, the functional relationships between the components of thecontacting device being determined so that is achieved within fractionsof a millisecond.

In the application of a contacting device which is constructed toachieve the above relationship, to a circuit interrupting duty, it isdesirable to maintain the movable contact in a disengaged position afterit has been moved thereto in order to prevent reclosure of thecooperating contacts.

One novel method of accomplishing this end is to further construct theunitary movable contact and operating winding so that it has a magneticmaterial at-. tached thereto. A magnetic means is then provided which isso disposed as to engage this magnetic material when the movable contacthas reached the full length of its travel. In the event that a biasingmeans is utilized to obtain contact pressure between the cooperablecontact, the seal in force of the magnet must be great enough toovercome this biasing force. However, upon engagement of this magneticmaterial by the above mentioned magnetic means which could be apermanent magnet, it is well known that the holding force or seal inforce is much greater than the normal forces acting at a distancebetween the magnet and magnetic material, and the contact will thereforebe rigidly maintained in the disengaged position.

Accordingly, another object of our invention is to provide a contactingdevice utilizing a unitary movable contact and winding which may be asingle short circuited winding wherein the movable contact device isfurther constructed to have a magnetic material attached thereto forlatching purposes.

Another object of our invention is to provide a means to maintain themovable contact of our novel contacting device in a disengaged positionafter it has been moved thereto.

A still further object of our invention is to provide the movablecontact of the above described contacting device with a magneticmaterial disposed for engagement with a permanent magnet when themovable contact is moved to a disengaged position.

We have further found that the operating winding and the movable contactwinding need not be two individual bodies but may in fact be componentsof an individual winding.

As is well known, a coil of wire carrying a current will tend tocontract. That is to say, there will be an attractive force between eachof the adjacent windings. If, however, a portion of the coil is wound ina first direction and the remainder of the coil is wound in an oppositedirection, then it is clear that there will be a repulsive force betweenthe oppositely wound portions of the coil. We propose to utilize thisprinciple by making the first portion a relatively stationary portion asby imbedding it in a relatively stationary body, and to utilize thesecond and oppositely wound portion as a movable contact member.Therefore, when the entire coil is energized, it is seen that themovable portion which is wound oppositely to the stationary portion willmove away from the stationary portion with an extremely highacceleration.

In this case, it is to be realized that for best results that the designshould be such that once again, the relationship given above should befollowed.

Accordingly, a still further object of our invention is to provide acontacting device of the above noted type wherein the operating windingand unitary movable contact winding are portions of the same windingwherein the stationary portion is wound in a first direction and themovable portion is wound in an opposite direction so that energizationof the complete winding will impart repulsive forces to the twoportions. 7

Another object of our invention is to provide a movable unitary contactand operating winding which are integral parts of a single winding.

These and many other objects of our invention will become apparent whentaken in conjunction with the following description in which:

1 Figure 1 shows one form which may be taken by an operating winding anda cooperating unitary movable body and winding whereby magneticinteraction between the two Winding effects relative motiontherebetween.

T Figure 2 shows an embodiment of an operating coil and a contactingstructure which may be driven to short circuit a pair of stationarycontacts.

Figure 3 shows an embodiment of a unitary movable contact and winding,which winding is a continuation of the operating winding, where theoperating winding and the contact winding are wound in oppositedirections. Figure 4 shows a still further embodiment of a contactdevice constructed in accordance with our novel invention asspecifically applied to a D.-C. circuit wherein magnetic latching meansare provided to latch the movable contact in a disengaged position.

' Figure 5 shows a still further embodiment of our novel invention asapplied to a vacuum switch.

Referring now to Figure 1, it is seen that an operating winding having anumber of turns N is positioned with respect to a movable winding 11having a number of turns N The winding 11 could, if desired, form themovable contact of a contact device and, in the case of Figure 1, it isshown as having two turns. The windings 10 and 11 of Figure l are thenshown as being separated by a separation of dimension a.

Capacitor 12 is then shown as being connectible in series with thewinding 10 by means of the switching device 13 which could be of anydesired type. Capacitor 12 is further shown as being maintained in acharged condition by means of the DC. source 14 which is connected inseries with the capacitor 12 and resistor 15.

In operation, when it is desired to impart motion to the winding 11, itis seen that one need only close the switch 13 to thereby allowcapacitor 12 to discharge through winding 10. The flow of currentthrough the winding 10, of course, produces a magnetic field which willthen induce a flow of current in the winding 11. This flow of current inthe winding 11 will in turn induce a second magnetic field and theinteraction between the two magnetic fields is then such as to cause arepulsion between the coils 10 and 11. Therefore coils 10 and 11 willmove away from one another at extremely high acceleration if a highdischarge current is obtained from capacitor 12.

It can be found with the application of the law of Biot-Savart, that theinstantaneous force between current carrying conductors which aredisposed as the conductors of Figure 1 is given by F 21rd (newtons)where The acceleration of the movable member may be expressed from thelaw of motion as where b=acceleration in meters per second squared m=mass of movable member in kilograms where m is any additional massattached to the movable member in kilograms.

Furthermore, m can be expressed as where: A is the cross-sectional areaof the movable conductor in square meters and g is the gravitationalconstant.

Since where: J is the current density in the movable conductor inamperes per square meter.

Hence, m may be written as m 7l'dI2 It now the relation for force F, andmass m are sub-' stituted into the equation of motion, it is seen that Ho h 1) J 9 Upon rationalization of the above equation, and dividing bothsides by g, it is seen that:

21raa'y It is to be noted that this relationship may be stated indifferent form.

One way for example uses the energy stored in the dischargable capactorwhich energizes the operating winding. If then:

where W==energy in the capacitor E=voltage on the capacitorC=capacitance of capacitor Since this energy is transferred to theoperating winding, one may write:

ICE

where: L is the inductance of the operating winding. If the inductanceis then expressed as:

where k and A are constants determined by the coil construction, then;

and

CE, (1''k) if the above expressions are then substituted into theequation of motion, the following relation is obtained:

where, in the term on the right, the first bracket contains theinvariable constants of the system, the second bracket expresses theavailable capacitor energy, and the third bracket describes the systemconstants.

By proper manipulation of a design, these constants must, in accordancewith our invention be chosen to give a value of b/ g of at least 10,000.

In the embodiment, of Figure 2, which shows a slightly modified form ofembodiment of Figure 1, it is seen that the operating winding 16 is nowcomprised of a fiat winding and the movable winding 17 is now comprisedof a single turn. Figure 2 further shows first and second relativelystationary contacts 18 and 19 which are so positioned as to be engagedby the movable winding 17 responsive to energization of the winding 16.These contacts may thereby be short circuited to protect faultedelectrical apparatus. In the case of Figure 2, it is seen that the aboveequation derived for the case of Figure 1 may be rewritten in a slightlymodified form:

I }lgJ S 9 2104 since a of the previous equation is now equal to:

where S is the radial width of coil 16.

For illustrative purposes only, it may be assumed that the distance xthrough which the movable contact of Figure 2 is to move is of amillimeter. An application of the above relationships would thereforeresult in a force of 600 kilograms and an acceleration of 40,000 timesthe acceleration due to gravity if, by way of example, the peakdischarge current in the coil 16 is 2,000 a'tnperes, the number of turnsof coil 16is 20, the dimension d or the mean diameter of the coil 17 isthree centimeters, the thickness S is cm., the dimension a is .26centimeter, the weight of the movable conductor kilogram, and thecurrent density is 300,000 amperes per square centimeter. In view ofthis result, it is seen that switching times of the order of 10 secondsmay be obtained, which time is sufiiciently short for operation of lowvoltage switch S.

If it is desired to apply or novel contacting device to a high voltageswitching device, then one need only utilize a medium of high dielectricstrength, such as a compressed gas or insulating liquid to assure thatthe instantaneous flash over voltage will always be greater than theinstantaneous recovery voltage across the separating contacts.

Figure 3 illustrates a still further embodiment of our novel inventionwhen the movable portion, which could be a movable contact, is comprisedof the portion 20 of the winding seen generally at 21, and the operatingwinding, which could be relatively stationary, is seen as windingportion 22. In operation of the device in Figure 3, the terminals 23 and24 of the winding 21 could be energizable by a charged capacitor in thesame manner as was the embodiment of Figure 1.

The embodiment of Figure 3 more specifically utilized the phenomenon ofa mutual attraction between adjacent turns of a coil when these turnsare wound in the same direction. If, by way of example, a stationarycontact were positioned on top of the movable portion Of the coil 20,then upon energization of the terminals 23 and 24 the complete coil willcontract and the mova ble portion 20 would move downward at highacceleration if high instantaneous currents are used.

In contradistinction, the movable portion of the coil 20 can have itswinding direction reversed as is shown in the figure, wherebyenergization of the coil 21 at the terminals 23 and 24 will then cause arepulsion between the winding portion 20 and the winding portion 22.Here again, this movement can be operative to bring the movable portion20 of the winding 21 into or out of engagement with a relativelystationary contact.

Insofar as the currents in the stationary and movable portions of thecontacting devices seen in Figures 1 through 3 have a phase oppositionof zero or degrees, either an attractive or repelling force occurs whichvaries in accordance with the instantaneous value of the mag* nitude ofthe currents in the coil. However, if the phase displacement can be madeto vary between the value of zero or 180 degrees, then it is seen thatforces with varying directional elfect may be produced.

By way of example, the force may start out as a repelling force and endup as an attractive force if the phase shift between the two currentsmay be sutficiently varied during motion of the movable conductor.

One can, therefore, take advantage of the electrodynamic forces for adeceleration as well as an acceleration. For example, in the case ofFigures 1 and 2, the production of phase shift offers no difliculties.That is to say, by inserting a suitable impedance in the movableconductors 11 or 17 of Figures 1 or 2 respectively, then a desired phasedisplacement may be obtained at a. desired time. This could thereforeresult in an extremely rapid acceleration of the movable member until apredetermined distance has been reached at which the forces due to themutual magnetic fields would be in a direction for deceleration of themoving member. By this means, the damping or stopping of the motion ofthe movable member may be considerably simplified and braking means maynot be needed.

Figure 4 shows the application of a contact device of the type shown inFigures 1 through 3 wherein specific application is made of a device ofthe type described herein to a D.-C. circuit, and the utilization of amagnetic latch means for maintaining movable contact in a disengagedposition is shown. Reference to Figure 4 shows a pair of stationarycontacts 25 and 26 which are bridged by a movable contact ring 27.

The movable contact ring 27 is more specifically constructed so as tohave a strip of ferro-magnetic material 28 attached thereto. Hence, inthe above described equation, the. quantity M would be the mass offerromagnetic strip 28.

A relatively stationary operating winding 29 is shown as beingpositioned in close coupling relationship with respect to the movablecontact ring 27, the operating winding 29 being chargeable by thecapacitor 30 which is maintained charged by means not shown in thedrawing. Capacitor 30, however, cannot discharge until ionization takesplace in the gap shown generally at 31 in order to connect theelectrodes 32 and 33 together.

In order to effect ionization at the gap 31, it is seen that atransductor device 34 is provided, having an air gap 35 therein. Thetransductor 34 more specifically has a winding 36 which is connected tothe DC. circuit being protected by the contact device. If then a reversecurrent occurs, it is seen that the transductor 34 which is normallysaturated in the direction given by the flow of load current I in thewinding 36 will have its flux reversed as D.-C. current decreasestowards zero and a voltage pulse will be induced in the winding 37.

This voltage pulse is impressed across the electrodes 32 and 38 tothereby initiate ionization in the gap 31 to thereby efiectively connectelectrodes 32 and 33 to connect the condenser 30 in series with theoperating winding 29 and the small inductor 39.

The energization of the coil 29, will, as has been previously described,induce a current in the movable contact ring 27 to thereby cause it tomove away from the relatively stationary operating winding 29 and hence,move the contact ring 27 to a disengaged position with respect to thestationary contacts 25 and 26.

If desired, the electrodes 32 and 33 may be connected manually orautomatically by the movable contact bridge 32a to thereby achieveinterruption of the contact device in the absence of reverse current inthe protected D.-C. circuit.

Figure 4 further shows a magnetic structure 40 which is so constructedas to have a plunger 41 extending therethrough and provides a supportmeans for a biasing spring 42 which may be adapted to maintain highpressure contact engagement between the movable contact ring 27 and itscooperating stationary contacts 25 and 26. Clearly, however, uponengagement of the ferro-magnetic strip 28 and the magnetic structure 40,seal in forces of relatively high magnitude will occur between themovable contact member 27 and the magnetic structure 40 to therebymaintain the movable contact structure 27 in the disengaged position inopposition to the biasing forces of spring 42.

When it is desired to return the movable contact 27 to its contactengaged position with respect to the stationary contacts 25 and 26,plunger handle 43 may be forced down to force the movable contactstructure away from the engaged position with the magnetic structure 40,when the biasing force of spring 42 will be sufiicient to move thecontact to the engaged position.

It is to be noted that the saturable reactor 34 is provided with an airgap 36 in order that the flux reversal may start at a time prior to thezero passage of current. In a tripping system of this type, it is thenseen that the instantaneous current interrupted by the movable contact27 and its cooperating stationary contacts 25 and 26 may be extremelysmall, and if, in the event an arc is drawn between the separatingcontacts, the arc will be extinguished when the current subsequentlypasses through the zero value.

Clearly, a similar arrangement to that of Figure 4 could have beenutilized for an alternating current circuit wherein the tripping systemis slightly modified to produce ionization in the air gap 31 responsiveonly to predetermined faults in the defective line as is shown in theabove mentioned application, Serial No. 558,349, filed January 10, 1956.

Figure shows a novel vacuum switch utilizing the same principles ofoperation as have been described with reference to each of the abovenoted Figures 1 through 4. In the case of vacuum switches, a highinitial force for contact separation is of great importance. Moreover,experience has shown that vacuum circuit breakers operate safely onlywhen the amount of material as operated from the contacts through thearc is as small as possible. Hence, an arcless operation for a vacuumcircuit breaker is greatly desirable and may be obtained in our novelhigh speed device in view of the extremely high accelerations impartedto the movable contact structure.

Figure 5 more specifically shows a semi-circular metallic housing 50into which relatively stationary conductors 5'1 and 52 are introducedthrough the vacuum tight insulating ducts 53 and 54. The ends of theconductors S1 and 52 act as stationary contacts 55 and 56 whichcooperate with the current bridge 57. The membrane 58 is connected in avacuum type manner to the flange 59 and has a cylindrical drum 60attached thereto. At the lower end of the cylindrical drum 60, thecurrent bridge 57 is attached, while the movable ring 62 is fastened tothe upper front surface through a connecting piece 61.

The stationary impulse winding or operating winding 63 is fused into thering shaped insulating piece 64 which in turn is attached to the flange59. A pin 65 is then led through the bearings 66 and 67 and is pressedagainst the ring 62 by the spring member 68. Hence, pin 68 is biased tomove into a position between the winding 63 and the ring 62 uponmovement of the ring 62 responsive to energization of the operatingwinding 63. Therefore, a reclosure of the contact bridge member 57 andits c0- operating stationary contacts 55 and 56 is prevented until, by adisplacement of the spring 68, the pin 65 is moved to the left of thering 62 and the membrane 58, under atmospheric pressure moves downwardto thereby reclose the circuit breaker.

In the foregoing we have described our invention solely in connectionwith specific illustrative embodiments thereof. Since many variationsand modifications of the invention will now be obvious to those skilledin the art, we prefer to be bound not by the specific disclosure hereincontained but only by the appended claims.

We claim:

1. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said stationary contact; said relatively movablecontact being constructed to form a first winding; an operating windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current flow therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect to said stationarycontact; said contacting device being further constructed to impart anacceleration of at least 10,000 times the acceleration due to gravityWithin a fraction of a millisecond after energization of said operatingwinding.

2. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said stationary contact; said relatively movablecontact being constructed to form a first winding; an operating windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current induced therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect to said stationarycontact; the quantity being at least 10,000.

3. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said stationary contact; said relatively movablecontact being constructed to form a first winding; an operating windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current induced therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect to said stationarycontact; said contacting device being further constructed to impart anacceleration of at least 10,000 times the acceleration due to gravitywithin a fraction of a millisecond after energization of said operatingwinding; a latching means; said latching means being constructed tolatch said movable contact in the disengaged position after said movablecontact is moved to said disengaged position.

4. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said stationary contact; said relatively movablecontact being constructed to form a first winding; an operating windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current induced therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect to said stationarycontact; said contacting device being further constructed to impart anacceleration of at least 10,000 times the acceleration due to gravitywithin a fraction of a millisecond after energization of said operatingwinding; said movable contact being further constructed to have magneticmaterial attached thereto; a magnetic structure; said magnetic structurebeing constructed to engage said magnetic material of said movablecontact when said movable contact is moved to said disengaged position;said movable contact thereby being latched in the disengaged position bythe seal-in force between said magnetic structure and said magneticmaterial attached to said magnetic material.

5. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said stationary contact; said relatively movablecontact being constructed to form a first winding; an operating windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current induced therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect to said stationarycontacts; the quantity being at least 10,000; said movable contact beingfurther constructed to have magnetic material attached thereto; amagnetic structure; said magnetic structure being constructed to engagesaid magnetic material of said movable contact when said movable contactis moved to said disengaged position; said movable contact thereby beinglatched in the disengaged position by the seal-in force between saidmagnetic structure and said magnetic material attached to said magneticmaterial.

6. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said stationary contact; said relatively movablecontact being constructed to form a first winding; an operating Windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current induced therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect tosaid stationarycontact; said contacting device being further constructed to impart anacceleration of at least 10,000 times the acceleration due to gravitywithin a fraction of a millisecond after energization of said operatingwinding;

said first winding being further constructed to have an impedanceconnected in series therewith whereby phase shift between the current insaid operating winding and the current in said first winding iseffected, the instantaneous force between said first winding and saidoperating winding being varied by variation in said phase shift.

'7. A contacting device; said contacting device comprising a continuousWinding of current carrying material; said continuous winding having afirst relatively stationary portion and a second relatively movableportion; said relatively movable portion being further constructed toform a relatively movable contact member; a relatively stationarycontact disposed for contact cooperation with said relatively movableportion; an energizing means; said energizing means being connectableacross said continuous winding, the passage of current through saidcontinuous winding causing relative motion between said first and secondportions of said winding; said relatively movable contact thereby movingin a predetermined direction with respect to said stationary contact.

8. A contacting device; said contacting device comprising a continuouswinding of current carrying material; said continuous winding having afirst relatively stationary portion wound in a first direction and asecond relatively movable portion wound in a direction opposite to saidfirst direction; said relatively movable portion being furtherconstructed to form a relatively movable contact member; a relativelystationary contact disposed for contact cooperation with said relativelymovable portion; an energizing means; said energizing means beingconnectable across said continuous winding; the passage of currentthrough said continuous winding causing repulsive forces between saidfirst and second winding portions; said relatively movable contactthereby moving in a predetermined direction with respect to saidstationary contact.

9. A contacting device; said contacting device comprising a stationarycontact and a relatively movable contact disposed for contactcooperation with said cooperating contact; said relatively movablecontact being constructed to form a first winding; an operating windingand an energizing means for passing current through said operatingwinding; said first winding being positioned with respect to saidoperating winding to have a current flow therein responsive to thepassage of current in said operating winding; the currents in said firstwinding and said operating winding being in a direction to move saidmovable contact to a disengaged position with respect to said stationarycontact; said contacting device being further constructed to impart anacceleration of at least 10,000 times the acceleration due to gravitywithin a fraction of a millisecond after energization of said operatingwinding, said operating winding and said first winding being continuouswith one another.

References Cited in the file of this patent UNITED STATES PATENTS363,186 Thomson May 17, 1887 953,584 Bishop et al Mar. 29, 19101,066,081 Coleman July 1, 1913 1,996,599 Thompson Apr. 2, 1935 2,180,661Baruch Nov. 21, 1939 2,389,999 Rypinski Nov. 27, 1945 2,499,394Kesselring Mar. 7, 1950 FOREIGN PATENTS 170,580 Switzerland Oct. 1, 1934

